Flare apparatuses in the form of a flare stack and one or more burners or ground-level flares in earthen pits are known and are used for burning combustible gases. Flare apparatuses are commonly used for disposing of flammable waste gases or other flammable gas streams in oil and gas production and refining, chemical plants, pipelines, liquefied petroleum and natural gas terminals, etc.
For example, oil and gas wells are tested by burning or “flaring” well fluid at the surface. The well fluid may be comprised of hydrocarbon gases, such as natural gas, oil and formation water. The term “wet gas” is commonly used for such well fluids. One problem associated with flaring of wet gas on offshore platforms is the radiant heat produced by flaring the wet gas and the effect of the radiant heat on the personnel and equipment disposed on the platform. Other problems include smoke formation and hydrocarbon fallout.
Specifically, it is generally desirable that the wet gas be flared without producing smoke and typically such smokeless or substantially smokeless flaring is mandated by regulatory agencies. Fallout of unburned hydrocarbons can occur when the wet gas being flared does not burn completely or cleanly. The resulting smoke and unburned hydrocarbon fallout may create both environmental and safety concerns as the unburned hydrocarbons may be disposed in liquid droplets that ultimately fall out of the ambient air onto the surface of the platform or the ocean.
Smokeless and fallout-free flaring of wet gas can be achieved by supplying additional air (i.e., air-assisted flaring) or steam (i.e., steam-assisted flaring) to the burner, which can result in a complete oxidation of the wet gas. However, at high flow rates of the wet gas, providing the optimal supply of air or steam for premixing upstream of the burner through pumps or blowers can become impractical or impossible, especially on offshore platforms or remotely located land-based drilling rigs. In contrast, when a highly turbulent jet of combustible wet gas is created in an open-air burner that does not require premixing, most of the requisite combustion air can be obtained from the ambient atmosphere near the flame. The design of such open-air burners is based on a maximum entrainment of ambient air into a high-pressure jet emitted through the burner head.
Further, the use of open-air burners for the combustion of wet gas would require spraying or atomizing of the liquid component that is carried by the input flow. The atomizing would be followed by mixing of the gas and atomized liquid with ambient air, which would create a mix suitable for clean flaring. While known atomizing nozzles are efficient if high-pressure gas and liquid flow are supplied through separate ducts, the wet gas for gas flaring at a rig site is a mixture of gas and liquid delivered to a flare apparatus together and in time-variable and unpredictable proportions. As a result, existing atomization nozzles cannot be used for oil and gas flaring without a gas/liquid separator, which is impractical for most offshore platforms and many land based well sites. Further, existing atomization nozzles are noisy, which adversely affects the safety and working environment of an offshore platform or a land-based well site.
Thus, wet gas burners are required that significantly reduce heat radiation and pollutants in the form of smoke and fallout that result from incomplete combustion, that can operate under a wide range of input pressures and that can operate with a reduced noise level.